1. Field of the Invention
This invention relates to a voltage-controlled current source contained in a semiconductor integrated circuit and a variable-gain amplifier using the same and more particularly to a circuit which compensates for the temperature dependency and process dependency and is used in the semiconductor integrated circuit.
2. Description of the Related Art
Generally, in a voltage-controlled current source contained in a semiconductor integrated circuit and outputting a current corresponding to an input voltage, the transfer conductance Gm has temperature dependency and process dependency. When the voltage-controlled current source is used in an amplifier, Gm of the voltage-controlled current source varies depending on temperature variation and process fluctuation, and therefore, there occurs a problem that the gain of the amplifier will vary.
In the amplifier subjected to temperature compensation in Jpn. Pat. Appn. KOKAI Publication No. 2000-244250, it is disclosed that the temperature dependency of the gain thereof is eliminated. In the temperature compensation circuit and variable-gain amplifier circuit in Jpn. Pat. Appn. KOKAI Publication No. 2002-141753, it is disclosed that temperature variation in the gain characteristic of the variable-gain amplifier is suppressed. Further, in the constant voltage generation circuit in Jpn. Pat. Appn. KOKAI Publication No. 2000-172353, a circuit configuration which permits sufficiently low reference voltage to be generated is disclosed. However, since the reference potential of the output circuit of the constant voltage generation circuit is fixed, there occurs a possibility that output voltage will fluctuate if the reference potential varies.